1. Field of the Invention
This invention relates to a resistor array board which is interposed between circuit forming elements such that a plurality of resistors are inserted between the elements.
2. Related Art
In general, for mounting conventional protective resistors, there is employed, among others, a method in which terminals of protective resistors are inserted into through-holes of circuit forming elements and the terminals are attached thereto by soldering. There is also employed a method in which a plurality of resistors are loaded on a board by soldering and the board is connected to circuit forming elements.
As means for mounting, as one group, a plurality of protective resistors, Japanese Patent Application Unexamined Publication No. H10-185989 discloses a method in which a plurality of protective resistors are molded to form a resistor package such that male terminals of the protective resistors project from opposite surfaces of the resistor package, and the male terminals are inserted into through-holes of circuit forming elements and soldered, and then the resistor package is mounted between the circuit forming elements.
However, the above-mentioned conventional methods have such problems that the work for inserting the protective resistors is complicated and time consuming. Moreover, in the latter method for mounting the resistor package into the through-holes, although the protective resistors can be mounted as one group, there are encountered such problems that the method cannot cope with a construction in which the opposite ends of the protective resistors are press contacted with the two circuit forming elements, the resistor package must be totally discarded when the protective resistor(s) is broken, and heat accumulation adversely affects electronic parts.
It is, therefore, an object of the present invention to provide a resistor array board, in which a plurality of protective resistors can easily be inserted as one group merely by interposing a resistor array board between circuit forming elements and opposite ends of the protective resistors can properly be press contacted with the circuit forming elements.
Another object of the present invention is to provide a resistor array board, in which a protective resistor(s) can easily be replaced when broken.
To achieve the above objects, a resistor array board according to the present invention comprises a porous plate having a plurality of through-holes arranged in array and opening at opposite surfaces thereof; and a plurality of protective resistors removably loosely inserted into the through-holes.
Each of the protective resistors is resiliently retained by each electrically conductive spring element, and opposite ends of each of the protective resistors are press contacted, either directly or indirectly, with each of circuit forming elements which are arranged in opposing relation on each surface of the porous plate.
Preferably, one end of the protective resistor is resiliently retained by the electrically conductive spring, one end of the protective resistor is press contacted with one of the circuit forming elements through the electrically conductive spring element and the other end of the protective resistor is press contacted with the other circuit forming element.
The porous plate is formed of a metal plate, and the resistor array board further comprises means for connecting the porous plate to a grounding line of one or both of the circuit forming elements, so that the means serves as a shield plate in which a shielding effect can be obtained by the porous plate.
The porous plate has a through-hole therein formed separately from the plurality of through holes in which the plurality of protective resistors are loosely inserted, a grounding contact is loosely inserted in the separately formed through-hole, the grounding contact is resiliently retained by the electrically conductive spring element, opposite ends of the grounding contact are press contacted, either directly or indirectly, with the circuit forming element by a resilient force of the electrically conductive spring element, and a grounding line is formed between the circuit forming elements.
The porous plate has a through-hole therein formed separately from the plurality of through holes in which the plurality of protective resistors are loosely inserted, a power supply contact is loosely inserted in the separately formed through-hole, the power supply contact is resiliently retained by the electrically conductive spring element, opposite ends of the power supply contact are press contacted, either directly or indirectly, with the circuit forming element by a resilient force of the electrically conductive spring element, and a power supply line is formed between the circuit forming elements.
Preferably, the porous plate is formed of a metal plate and an inner peripheral surface of the through-hole for allowing the protective resistor of the porous plate to be loosely inserted therein is coated with an insulative material.